In the course of treating and preparing subterranean wells for production, a well packer is run into the well on a work string or a production tubing. The purpose of the packer is to support production tubing and other completion equipment, such as a screen adjacent to a producing formation, and to seal the annulus between the outside of the production tubing and the inside of the well casing to block movement of fluids through the annulus past the packer location. The packer is typically provided with anchor slips having opposed camming surfaces which cooperate with complementary opposed wedging surfaces, whereby the anchor slips are radially extendible into gripping engagement against the well casing bore in response to relative axial movement of the wedging surfaces.
The packer also carries annular seal elements which are expandable radially into sealing engagement against the bore of the well casing. Longitudinal movement of the packer components which set the anchor slips and the sealing elements may be produced either hydraulically or mechanically.
After the packer has been set and sealed against the well casing bore, it should maintain sealing engagement upon removal of the hydraulic or mechanical setting force. Moreover, it is essential that the packer remain locked in its set and sealed configuration while withstanding hydraulic pressure applied externally or internally from the formation and or manipulation of the tubing string and service tools without unsetting the packer or interrupting the seal. This is made more difficult in deep wells in which the packer and its components are subjected to high downhole temperatures, for example temperatures up to and exceeding 400xc2x0 F., and high downhole pressures, for example, 5,000 pounds per square inch (xe2x80x9cpsixe2x80x9d). The packer should be able to withstand variation of externally applied hydraulic pressures at levels up to as much as 15,000 psi in both directions.
There are packers that are designed to withstand such extreme conditions, but such packers are intended to be set and left in the hole for a long period of time. For example, U.S. Pat. No. 5,944,102 to Kilgore et al. is directed to a high temperature high pressure retrievable packer which is designed to be utilized in wells with extreme conditions and to be retrievable after exposure for long periods. The packer disclosed therein is not, however, suited to be set in the hole, unset and reset repetitively in the well. U.S. patent application Ser. No. 09/083,304 (the ""304 application) directed to RETRIEVABLE HIGH PRESSURE HIGH TEMPERATURE PACKER APPARATUS WITH ANTI-EXTRUSION SYSTEM and assigned to the assignee of the present invention, the details of which are incorporated herein by reference, discloses an embodiment of a high pressure high temperature packer apparatus that can be set, unset and reset in the well and will maintain a seal each time it is reset. With conventional mechanical slips, like that shown in the ""304 application, load applied in high temperature high pressure packer settings is such that the casing can be damaged. The conventional slip shown therein makes deep penetration marks in the casing, which can negatively impact the casing integrity and the life of the casing. Thus, there is a continuing need for a high temperature, high pressure packer which can be set and reset a number of times and which will lessen casing damage each time the packer is set.
The present invention provides a retrievable packer apparatus that can be alternated between set and unset positions in a wellbore and can maintain sealing engagement with casing disposed in the wellbore each time it is set at temperatures as high as and exceeding 400xc2x0 F. and pressures as high as 15,000 psi. The packer apparatus includes a barrel slip and a mechanical slip that will engage and hold the packer apparatus in the wellbore while minimizing any damage to the casing from the slip engagement with the casing. The apparatus further includes a novel liner lock to prevent the packer apparatus from prematurely moving from an unset to a set position.
The packer apparatus includes a packer mandrel and has a seal assembly disposed about the packer mandrel. The packer apparatus further includes a barrel slip and a mechanical anchor slip disposed about the mandrel below the seal assembly. Upper and lower barrel slip wedges are disposed about the packer mandrel above and below the barrel slip. The upper and lower barrel slip wedges are capable of applying load transmitted thereto to the center of the barrel slip such that the barrel slip will be expanded radially outwardly so that it will engage casing in the wellbore. The mechanical slip is disposed about the packer mandrel below the barrel slip. The purpose of the lower mechanical slip is to offer initial grip to the casing so that the barrel slip can be engaged to grip the casing to hold the tool when high loads are applied.
The barrel slip includes a barrel slip body having a plurality of openings defined in an outer surface thereof A plurality of inserts are received in the barrel slip body. The openings are oriented such that the inserts define a plurality of upward facing and downward facing gripping edges. Thus, once the barrel slip is expanded radially outwardly, the inserts will engage the casing in the well and the barrel slip will prevent both upward and downward movement in the well. The radial expansion of the barrel slip is described in more detail in U.S. Pat. No. 5,944,102 (the ""102 patent) to Kilgore et al. issued Aug. 31, 1999, the details of which are incorporated herein by reference. The barrel slip body has a sufficient number of inserts disposed along the length and about the circumference thereof such that the barrel slip will get a good grip in the casing and will spread the slip to casing load over a large area to minimize slip. to casing contact stresses.
Prior to the setting of the barrel slip, downward movement of the mandrel will cause the mechanical slip to engage the casing. Inadvertent or premature setting of the mechanical and barrel slips is prevented by a liner lock which is operably associated with a drag block assembly disposed about the mandrel below the mechanical slip. The liner lock comprises an arm pivotably attached to the drag block sleeve. The arm engages the mandrel when the packer apparatus is in an initial running position. Compression of the drag block sleeve will cause the arm to pivot and disengage from the mandrel so that the packer mandrel can move to cause radial expansion of the mechanical slip, barrel slip and seal assembly to move the packer apparatus into its set position. The packer apparatus can be moved between its set and unset positions as many times as desired prior to removing the packer apparatus from the well. Each time the packer apparatus is moved to its set position, the mechanical and barrel slip will engage the casing to hold the apparatus, and whatever is attached thereto in the well, and the seal assembly will seal against the casing.
The novel features of the invention are set forth with particularity in the claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.